Toán Lớp 8: tìm x
a,( x – 3 )( x ² +3x +9 )+ x ( x+2 )(2 – x)=0
b,(x + 1 ) ³ – ( x-1) ³-6(x-1) ²= -10
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Toán Lớp 8: tìm x
a,( x – 3 )( x ² +3x +9 )+ x ( x+2 )(2 – x)=0
b,(x + 1 ) ³ – ( x-1) ³-6(x-1) ²= -10
giúp em với em cần gấp
Comments ( 2 )
<=>x^3-3^3+x(2-x^2)=0
<=>x^3-27+2x-x^3=0
<=>2x=27
<=>x=27/2
<=>x=13,5
Vậy x in {13,5}
b)(x + 1 ) ³ – ( x-1) ³-6(x-1) ²= -10
<=>x^3+3x^2+3x+1-(x^3-3x^2+3x-1)-6(x^2-2x+1)=-10
<=>x^3+3x^2+3x+1-x^3+3x^2-3x+1-6x^2+12x-6=-10
<=>12x-4=-10
<=>12x=-6
<=>x=-1/2
Vậy x in {-1/2}